According to Burrell, Diana would have liked to marry Khan, but the Pakistan-born transplant surgeon broke off their relationship. "I think there were too many complications on both sides," Burrell said in the 20/20 interview, which will be aired on Friday, Oct. 24. "The princess always said she came with a lot of baggage."

It was shortly after the relationship ended that Diana met Fayed, the son of Mohammed Al Fayed, the owner of London's exclusive store Harrods.

In his new book, A Royal Duty, Burrell has made a number of startling revelations about Diana's life as well as her emotional state months before her 1997 death in a Paris car crash.

Burrell said Diana sent him a handwritten note claiming she "never wanted a divorce" from Prince Charles.

"She still wanted to work with the marriage," Burrell told Walters. "There's a bit of her that always loved the prince until the day she died."

Searching for Bugs in Sitting Room

The interview also reveals that Diana sent Burrell a letter 10 months before the deadly Paris crash, in which she predicted her own death, claiming that someone was planning a car accident in which she'd be killed.

The British government has so far rejected calls for a public inquiry into her death. However, a coroner's
inquest is expected to be held once legal processes in France have been completed.

In 1999, a French investigation ruled the crash was an accident caused by the chauffeur being drunk and driving
too fast.

When asked about the reasons why Diana would have feared for her life, Burrell said the princess was frightened for her own security because the royal family considered her a "loose cannon."

"She talked rather a lot to a lot of people," said Burrell. "She trusted psychics and confidants, and I think they just wanted to keep her quiet."

He described one incident where the princess was convinced there were electronic listening devices — "bugs" — placed in her sitting room.

"She was paranoid about all other aspects of security in her life," he said. "One afternoon I went up to her sitting room, we rolled back the carpet and moved all the furniture and pulled up the floor boards trying to find listening devices."

There were no bugs found in the room.

Queen: Be Careful, Paul

But Burrell also confirmed that he was worried about his own security these days.

Last year, a case against Burrell accusing him of theft of royal property collapsed after an unprecedented intervention by Queen Elizabeth, who recalled a conversation with Burrell during which the butler mentioned that the items were with him for safekeeping.

Speaking about the advice the Queen had allegedly given him, Burrell said the British monarch had warned him "to be careful. She said that there are powers at work in this country of which we have no knowledge," he said "She was telling me, 'Be careful, Paul.'"

And when asked about why he was disclosing Diana's private letters to the public more than six years after her death, Burrell said it was because he thought it was "important" to place them in the public domain.

"I struggled so long and so hard with this, wondering what to do with it," he said. "I didn't know what to do with it. If I gave it to the wrong person, it could be shredded. It could be erased. It could disappear … I think it's an important letter. I think now it's there in the public domain, and now we will have a proper investigation into her death."